〜て以来
ever since
Verb て-form + 以来 · Noun + 以来
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以来 means "since then, ever since": 日本に来て以来、ずっと東京に住んでいる, "I've lived in Tokyo ever since I came to Japan".
After a verb it follows the て-form; after a noun it attaches directly: 卒業以来, "since graduation"; あの日以来, "since that day".
The second part is a state that has continued from that point until now: living somewhere, not having seen someone, being afraid of something. That's the difference from てから, which just gives an order ("after"). 以来 insists on "and it has been that way ever since".
It's a little formal. In conversation, てから、ずっと often does the same job.
Examples
日本に来て以来、ずっと東京に住んでいる。
I've lived in Tokyo ever since I came to Japan.
卒業以来、彼には会っていない。
I haven't seen him since graduation.
事故にあって以来、車の運転が怖い。
Ever since the accident, I've been afraid of driving.
子どもが生まれて以来、生活が変わった。
Life has changed ever since our child was born.
あの日以来、彼女とは話していない。
I haven't spoken to her since that day.